With the development of information technologies, people are highly dependent on electronic devices. For meeting the requirements of high speed, high performance and small size, portable electronic devices with a camera function become the mainstream of the modern electronic products and become the indispensable tools of the modern lives. Consequently, the applications of various image pickup devices (e.g., conventional cameras, digital cameras or mobile phones with an imaging function) are gradually expanded. For enhancing the imaging function, the image pickup device is usually equipped with a flashlight device. While the image pickup device is used in photography, the flashlight device produces a flash of artificial light to help illuminate an environment. Consequently, the captured image is more shape.
FIG. 1 is a schematic view illustrating the structure of a conventional flashlight device. As shown in FIG. 1, the flashlight device 1 comprises a flash lens 12 and a light source 11. For example, the light source 11 is a light emitting diode. The light source 11 provides light beams L1. The flash lens 12 has a saw-toothed structure 121 that faces the light source 11. After the light beams L1 from the light source 11 pass through the flash lens 12, the light beams L1 are outputted from the flash lens 12. Since the travelling direction of the light beams L1 is changed by the saw-toothed structure 121, the outputted light beams L1* are diffused to fill light to the environment.
However, the efficacy of filling light by the conventional flashlight device 1 is usually unsatisfied because the light beams L1* outputted from the flash lens 12 are not uniformly diffused and the brightness values in various positions of the environment are not completely identical. For solving these drawbacks, many technologies have been disclosed. For example, US Patent Publication No. US2012/0176801 and US Patent Publication No. 2014-0226299 disclose the technologies of uniformly outputting the light beam of the light source by changing the structure of the flash lens. Due to the limitation of the outer appearance of the flash lens, the excessively-curved surfaces cannot be used. Nowadays, the trend of designing the flashlight device is toward the combination of the flash lens and an associated mechanism. Under this circumstance, the mechanism to be combined with the flash lens should have a supporting surface corresponding to the flash lens. Because of the supporting surface, the lighting surface of the flash lens is limited. If the lighting surface of the flash lens is not limited, the flash lens cannot be combined with the mechanism. That is, because of the demands on the outer appearance and the mechanical strength and the limitation of the producing process, the flash lens with the changed structure is not satisfied and usually detrimental to competiveness or mass production. Moreover, since the thickness of the flash lens is not effectively reduced, the flashlight device cannot meet the requirements of small size, light weightiness and easy portability.
Moreover, US Patent Publication No. US2012/0018322 discloses a technology of increasing the light uniformity by installing an optical diffusion structure on an outer case (e.g., a mobile phone case) at a position corresponding to the flash lens. However, due to the limitation of the producing process, the precision of the outer case cannot match the flash lens. Moreover, U.S. Pat. No. 5,477,292 discloses a method of increasing the uniformity of the outputted light beams by installing a slidable diffusion plate in front of the flashlight device. However, the complexity of the mechanism and the overall thickness of the flashlight device are increased.
Moreover, as the demands on the imaging quality gradually increase, the color (i.e., the color temperature) of the image captured by the image pickup device should be as vivid as possible. Consequently, the user is fastidious about the fidelity of the color temperature of the flashlight device. Moreover, since the flashlight device 1 as shown in FIG. 1 only has a single light source to generate a flash of light (i.e., a single flash), the color saturation of filling light to the environment by the flashing device is usually insufficient and the color temperature fails to be adjusted. For solving these drawbacks, another conventional flashlight device is further equipped with a second light source (i.e., a twin flash) or even a third light source (i.e., a triple flash). However, since plural light sources of the flashlight device do not have the same lighting center, it is an issue of providing a method of uniformity outputting the light beams while mixing the color temperatures and mixing the optical intensities.
Moreover, the blue light contained in the light source of the conventional flashlight device, for example a light emitting diode (LED), accounts for a greater fraction of the light spectrum. Since the blue light is usually not acceptable to many users or the environment, it is also an important issue to convert a portion of the blue light into the acceptable light.
From the above discussions, the conventional flashlight device needs to be further improved.